以京农科728为试验材料，在相同施肥量条件下，设置4个矮壮素（CCC）施用梯度，通过与氮肥拌肥处理一次性基施，研究矮壮素对华北夏玉米产量、氮代谢及氮素利用率的影响。结果表明，相对常规氮肥处理，CCC处理增加了玉米产量、千粒重和穗粒数，干物质积累量在花期之后显著增加，叶面积指数显著高于常规氮肥对照；增强了叶片硝酸还原酶（NR）、谷氨酰胺合成酶（GS）及花后34 d至收获期的谷丙转氨酶（GOT）等氮代谢酶活性，提高了叶绿素总含量和可溶性蛋白含量。氮素利用率得到了提高，最佳施用量是675 kg/hm²，在最佳施用量下，氮肥偏生产力、氮肥农学效率和氮肥生理利用率分别比常规氮肥对照增加5.4%、45.8%和22.7%。

Using Jingnongke728 as the test material, under the same fertilizer application conditions, four CCC treatments were set, and a one-time basic application of mixed fertilizer treatment with nitrogen fertilizer was conducted to study the effects of chlormequat on the yield, nitrogen metabolism and nitrogen utilization of summer maize in North China. The results showed that compared with conventional nitrogen fertilizer treatment, CCC treatment increased maize grain yield, 1 000-kernel weight and kernel number, post-silking aboveground dry matter accumulation significantly, and the leaf area index as well, enhances the leaf nitrogen-metabolizing enzyme activities such as nitrate reductase(NR), glutamine synthetase(GS), increase the total chlorophyll content and soluble protein content. The nitrogen utilization rate was improved. The optimum application rate was 675 kg/ha. Under the optimal application amount, partial productivity of nitrogen fertilizer, agronomic efficiency of nitrogen fertilizer and physiological utilization rate of nitrogen fertilizer had increased by 5.4%, 45.8% and 22.7%, respectively compared to CK. This study showed that CCC mixed with nitrogen fertilizer could mobilize the key enzyme activity of nitrogen metabolism, thus enhance the metabolism of nitrogen, thus improving the utilization rate of nitrogen and achieving high yield.

新型高效植物生长调节剂和生物除草剂研发项目（2017 YFD0201301）、横向合作项目（2016110001000035）